Hydration Characteristics and Mechanical Properties of Cement-Based Materials Modified by Calcined Zeolite and Montmorillonite

Montmorillonite and clinoptilolite zeolite were used as representative materials to prepare calcined clay-cement binary cementitious materials in order to study the effect of calcination treatment on the activation of clay minerals and the activity difference between layered and framed clays in this research.The influence of different calcined clay content(2%,4%,6%,8%,10%)on the fluidity,compressive strength,microstructure,phase change,and hydration heat of cement-based materials were analyzed.The calcined clay improves the fluidity of cement-based materials as compared with the uncalcined group.The addition of calcined montmorillonite(CMT)improves the development of mechanical strength,and the optimal compressive strength reaches 85 MPa at 28 days with 8%CMT.However,the activity of calcined clinoptilolite zeolite(CZL)is weak with few reaction sites,which slightly reduced the mechanical strength as compared to the blank sample.The addition of CMT changes the microscopic morphology of hydration products such as C-S-H and C-A-H,leading to the formation and transformation of ettringite in the early stage.It promotes the gradual polymerization of Si-O bonds into Si-O-Si bonds simultaneously,which accelerates the early hydration process.However,CZL acts mainly as a filling function in the cementitious system.In brief,CMT as an admixture can improve the mechanical properties of cement,but CZL has little effect.This work provides a guideline for the applications of calcined clay in cement,considering the influence of clay type on workability and mechanical strength.

A Comparative Study of Transesterification of Hydnocapus weightiana Seed Oil Using Calcined and Acid Activated Natural Heterogeneous Catalyst and Its Kinetic Study

The world’s total fossil fuel consumption has been significantly increasing with consequential increased environmental catastrophes. A hunt for an alternate energy source was stimulated. Biofuel is a plausible option in this pursuit due to its ideal qualities which included but are not limited to renewability and environmental friendliness. However, the pump price of biodiesel is still very high due mainly to the high cost of the production of the commodity which is influenced by the feedstock and the homogeneous nature of catalyst used. Heterogeneous catalyst was prepared by using Pila globosa sea snail shells prepared by calcination (CP8) and by acid activation (PTW1M). Hydnocapus weightiana seed oil (Non-edible feedstock) was extracted using the soxhlet extraction method and was used for biofuel production with a methanol oil ratio of 3:1. Agitation speed 800, 600 rmp, reaction temperatures of 70°C, 60°C, catalyst concentration (3.00, 2.00 wt%) and reaction time (70 and 60 min) was maintained for CP8 and PTW1M respectively. The rate of the reaction followed a reversible second-order reaction rate. Re-usability accessed. From TGA analysis, the best calcination temperature was 800°C. SEM results showed improved surface morphology after calcination, especially for CP8. FTIR analysis showed the elimination of volatiles and formation of CaO and CaO4Te after calcination. The reaction rate constant at different temperatures was 0.0287 at 30°C, 0.1200 at 50°C and 0.1142 at 70°C and activation energy of the ethyl ester was 49.49 KJ/mol. Using CP8. Most of the fuel properties met with ASTM 6751 standard. The result of the re-usability showed that the biodiesel yield declined as follows: 92, 86, 80, 73 and 69 % for CP8 and 85, 84, 81, 76, 65. For PTW1M. After the fifth regeneration cycle, both CP8 and PTW1M samples of Pila globosa sea snail shell catalyst proved effective in transesterification reaction of Hydnocapus weightiana seed oil using ethanol. It was observed that the calcined catalyst (CP8) showed a superior catalytic performance.

Production of an Eco-Cement by Clinker Substitution by the Mixture of Calcined Clay and Limestone, Songololo (DR Congo)

Ordinary Portland Cement (OPC) is by mass the largest manufactured product on Earth, responsible for approximately 6% - 8% of global anthropogenic carbon dioxide emissions (CO2) and 35% of industrial CO2 emissions. On average 0.8 to 0.9 ton of CO2 is emitted to produce one ton of OPC. In this paper, partial substitution of clinker (30% - 35%) by the calcined clay-limestone mixture was investigated in order to produce an eco-cement (LC3). Analyzes by XRF, XRD and ATG/ATD have characterized different components, determined the calcination temperature and selected the right clay which can act as effective Supplementary Cementitious Material (SCM). Mechanical tests on mortar carried out over a period of 90 days. The WBCSD/WRI “Greenhouse Gas Protocol” methodology then allowed the calculation of CO2 emissions into the atmosphere. Three types of clay are available in the Songololo Region. The kaolinite is the principal clay mineral and its content varies from 27% to 34%. The sum of kaolinite and amorphous phase which enable clay to react with cementitious material ranges from 57% to 60%. The SiO2 content ranges from 33% to 76%, the Alumina content from 12% to 20% so that the ratio Al2O3/SiO2 is on the higher side (0.17 - 0.53). The calcination window is between 750°C and 850°C and the best clay which can act as SCM identified. The clinker’s substitution reduced CO2 emissions from 0.824 ton of CO2 for one ton of OPC to 0.640 ton of CO2 for one ton of LC3, means 22% less emissions. The compressive strengths developed by LC3 vary from 8.91 to 57.6 MPa (Day 1 to Day 90), exceed those of references 32.5 cement and are close to 42.5 cement. In view of the results, LC3 cement can be considered for industrial trials.

Properties and Hydration Mechanism of Cementitious Materials Prepared from Calcined Coal Gangue

The preparation of cementitious materials by replacing part of the cement with activated coal gangue is of great significance to the cement industry in terms of carbon reduction and coal-based solid waste utilization.For this paper,cementitious material was prepared by firing activated coal gangue under suspension conditions and batching it with limestone powder using Inner Mongolia coal gangue as raw material.The optimal ratio was determined by testing the strength changes of the cementitious material at 3,7,and 28 days of hydration,and the hydration process and mechanism were explored by combining the pore structure,heat of hydration,chemical composition,phase composition,and microscopic morphological characteristics of the hydration products.The results showed that the active materials formulated from activated gangue and limestone powder can be used to prepare cementitious materials with good performance at the level of 30%–50%replacement of cement.The optimal ratio was 30%replacement of cement,and the mass ratio of calcined gangue to limestone powder was 2:1.The 3 days compressive strength of this ratio was 28.8 MPa,which was only slightly lower than that of cement.However,the 28 days compressive strength of samples reached 67.5 MPa,which was much higher than that of the reference cement.In the hydration of this cementitious material,not only does the activated coal gangue react with the Ca(OH)_(2)formed by hydration to form C–S–H gel,but CaCO3 also participates in the reaction to form a new phase of carbon aluminate,and the two effects together promote the development of the later strength of the samples.This paper can provide a reference for carbon reduction in the cement production process and comprehensive utilization of coal gangue.

Adsorption of glutamic acid from aqueous solution with calcined layered double Mg-Fe-CO_3 hydroxide

Layered double Mg-Fe-CO3 hydroxide （Mg-Fe-LDH） with a mole ratio of Mg to Fe of 3 was synthesized by coprecipitation method and calcined product Mg-Fe-CLDH was obtained by heating Mg-Fe-LDH at 500 ℃ for 6 h. The as prepared Mg-Fe-LDH and calcined Mg-Fe-CLDH were used for removal of glutamic acid （Glu） from aqueous solution, respectively. Batch studies were carried out to address various experimental parameters such as contact time, pH, initial glutamic acid （Glu） concentration, co-existing anions and temperature. Glu was removed effectively （99.9%） under the optimized experimental conditions with Mg-Fe-CLDH. The adsorption kinetics follows the Ho’s pseudo second-order model. Isotherms for adsorption with Mg-Fe-CLDH at different solution temperatures were well described using the Langmuir model with a good correlation coefficient. The intraparticle diffusion model fitted the data well, which suggests that the intraparticle diffusion is not only the rate-limiting step.

Potential for Use of Iron Mining Tailings Calcined in a Flash Furnace as Pozzolanic Material

This paper presents a study of the potential use of iron mining tailings as artificial pozzolan (metakaolin) after their submission to thermal treatment via calcination in a flash furnace. The research consists of the characterization of the tailings before and after calcination, chemical, mineralogical, thermogravimetric, and mechanical strength analyses were conducted. The results were compared with those for commonly used pozzolans, metakaolin, and similarities were identified. The study of the morphology of the particles before and after calcination was conducted through analyses of images obtained by scanning electronic microscope. The pozzolanic activity of the fine mining tailings calcined with flash technology was evaluated in uniaxial compression trials, which showed excellent results.

Preparation and mechanical properties of polypropylene fiber reinforced calcined kaolin-fly ash based geopolymer

To improve the environmental benefits and solve the problems of large shrinkage and high brittleness, the partial replacement of calcined kaolin by fly ash as a raw material for geopolymer synthesis and the influences of polypropylene (PP) fiber on the mechanical properties and volume stability were investigated. The results show that compressive strength of the geopolymer containing 33.3%(mass fraction) fly ash by steam curing at 80 ℃ for 6 d is improved by 35.5%. The 3-day compressive strength, flexural strength and impacting energy of geopolymers containing 0.05%PP fiber increase by 67.8%, 36.1% and 6.25%, while the shrinkage and modulus of compressibility decrease by 38.6% and 31.3%, respectively. The results of scanning electron microscopy (SEM) and the appearances of crack growths confirm that PP fiber can offer a bridging effect over the harmful pores and defects and change the expanding ways of cracks, resulting in a great improvement of strength and toughness.

Effect of Heat Treatment Temperature on Properties of Chinese Calcined Flint Clay Based Plastic Refractories

Effects of different heat treatment temperatures on properties of Chinese calcined flint clay based plastic refractories were investigated using Chinese calcined flint clay as starting material, aluminum sulfate and fireclay as binding system. The results showed that with temperature rising, Chinese calcined flint clay based plastic refractories shrinked firstly and then expanded. The modulus of rupture （MOR） and the cold crushing strength （CCS） inereased firstly and then decreased from 110 ℃ to 600 ℃ , then increased obviously. Thermal expansion coefficient increased from 110 ℃ to 760 ℃, decreased from 760 ℃ to 1 300 ℃ , and increased from 1 300 ℃ to1500 ℃.

Synthesis of Refractory Cordierite from Calcined Bauxite, Talcum and Quartz

A cordierite was synthesized from calcined bauxite, talcum, and quartz. The properties and microstructure of the cordierite sintered samples were characterized by Archimedes＇ method, thermal dilatometry, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and so on. The experimental results showed that calcined bauxite could broaden the range of synthesizing temperature from 1300 ℃ to 1420 ℃ and get pure cordierite. The bulk density and linear thermal expansion coefficient of the sample synthesized at 1420 ℃ for 2 h were 1.97 g·cm^-3 and 2.1×10^-6 ℃^-1, respectively. The XRD analysis showed that the major crystalline phase was a-cordierite with almost no glassy matters, the SEM images illustrated a small vent hole and the size were 5 -100 μm, the well-grown hexagonal and granular cordierite grains had the sizes distributed among 0.1-8 ;xm, and providing high mechanical strength and lower linear thermal expansion coefficient.

Characterization of Calcined Kaolin/TiO_2 Composite Particle Material Prepared by Mechano-Chemical Method

Calcined kaolin/TiO2 composite particle material （CK/TCPM） was prepared with TiO2 coating on the surfaces of calcined kaolin particles by the mechano-chemical method. X-ray diffraction （XRD） and scanning electron microscope （SEM） were used to investigate the microstructures and morphologies, respectively. The mechanism of the mechano-chemical reaction between calcined kaolin and TiO2 was studied by infrared spectra （IR）. The results show that TiO2 coats evenly on the surfaces of calcined kaolin particles by Si-O-Ti and Al-O-Ti bonds on their interfaces. The hiding power and whiteness of CK/TCPM are 17.12 g/m^2 and 95.7%, respectively, presenting its similarity to TiO2 in pigment properties.

Dissolution properties of calcined gangue

To study the dissolution mechanism of gangue, dissolution characteristics of the gangue samples calcined at different temperatures in alkaline solutions and alkali metal silicate solutions with respect to Si and Al ions were analyzed by identical coupled plasma optical emission spectroscopy （ICP）. The results show that the extent of dissolution of Al and Si varies with calcination temperature. It shows that the samples have a higher degree of dissolution in NaOH than in KOH medium. Si and Al appear to have synchro-dissolution behavior in alkaline solution, which means that Si and Al could dissolve from the mineral surface in certain linked forms. The result that a higher degree of dissolution exists in sodium silicate solution and a lower degree of dissolution exists in sodium-potassium silicate solution of Al is proved by the 29Si NMR spectra and the mean connectivity degree of these alkali metal silicate solutions.

The Adsorbing Effect of Calcined Layered Double Hydroxide for Chloride Ions in Simulated Concrete Pore Solutions

The adsorbing effect of calcined layered double hydroxide （CLDH） for chloride ions in simulated concrete pore （SCP） solutions was investigated with the potentiodynamic polarization method, impedance measurement, ion selective electrode analysis and XRD. CLDH could effectively adsorb Cl^- and increase pH value in SCP solutions containing NaCl. The chloride to hydroxyl ions ratio （[C1^-]/[OH^-]） of the solution greatly decreased by CLDH treatment. In CLDH treated SCP solution with CI-, the pitting potential of carbon steel notably increased, and the surface impedance was much higher, indicating strengthened passivation. The process of CLDH adsorbing chloride ions from SCP solutions was accompanied with the reconstruction of the layered structure.

Sulfate Ions Immobilization of Calcined Layered Double Hydroxides in Hardened Cement Paste and Concrete

The sulfate ions immobilization behavior of calcined layered double hydroxides(CLDHs) in the hardened cement paste was investigated. The experimental results show that the sulfate ions in cement paste are immobilized by CLDHs to reconstruct the layered structure and aggregate around CLDHs. The immobilization amount of sulfate ions by CLDHs reaches 4.74×10^-3 mol/g, while the increasing amount indicates non-linear relation with the addition of CLDHs. The incorporation of CLDHs decreases the amount of ettringite formed to limit the expansion of cement paste, which decays the sulfate reaction to enhance the sulfate resistance of concrete.

Coating mechanism of nano-TiO_2 films on the surface of ultra-fine calcined coal kaolin particles

A new type of mineral composite was made by calcined coal kaolin.The interaction mechanism of an inorganic modification reagent TiOSO4 with the surface of ultra-fine calcined coal kaolin particles（substrate） was studied by X-ray photoelectron spectroscopy.The results show that chemisorption exists in the phase boundary between the modification agent and the substrate surface,while physical adsorption occurs on the modification layers of hydrate titanium dioxide.The interaction force was calculated and analyzed according to DLVO theory between ultra-fine calcined coal kaolin particles and hydrate titanium dioxide nano-particles in the modification system.It is shown that the both electrostatic force and van der Waals force are attractive,and the coacervation between ultra-fine calcined coal kaolin particles and hydrate titanium dioxide nano-particles leads to the coating of hydrate titanium dioxide on the surface of ultra-fine calcined coal kaolin particles.

Removal of Cu(Ⅱ) From Aqueous Solutions Using Colloidal Pyrite Calcined Under Inert Atmosphere

A natural colloidal pyrite calcined in N2 atmosphere was utilized to remove Cu(II) from aqueous solutions in present work. Effect of calcination temperature, initial solution pH, reaction time, initial Cu(II) concentration, sorption temperature, foreign ions and the dissolved oxygen (DO) on Cu(II) removal was investigated. The results showed that colloidal pyrite calcined at 500-550°C (CCPy) has a most promising potential for Cu(II) removal. The increase of pH, initial Cu(II) concentration and reaction time benefited the improvement of Cu(II) removal efficiency. The isothermal adsorption data of CCPy was well described by Langmuir isotherms and the thermodynamic parameters (ΔG<0, ΔH>0), indicating the endothermic nature of Cu(II) sorption on CCPy. The presence of most common ions in acid mine drainage and DO just had little influence on the Cu(II) uptake. The observation implied that CCPy is a low-cost, abundant material for Cu removal from Cu waters.

Mechanism of Calcined Phosphogypsum for the Volume Change of Blended Cement

The paper describes an investigation into the volume change of cement mortar specimen at the three kinds of different curing schedules including 20℃and 5% Na2SO4 solution curing, tap water standard curing, 50% RH curing for 90 days. The testing results of hydration heat, chemical shrinking and XRD prove that calcined phosphogypsum has evident excitation effect on the activity of high calcium ash and steel slag. Simultaneously, calcined phosphogypsum has the function of decreasing volume shrinkage to blended cement possessing steel slag and high calcium ash. In sulfate curing, calcined phosphogypsum can avoid the phenomenon of protrude apex of the blended cement.

Studies of the Catalytic Activity and Deactivation of Calcined Layered Double Hydroxides in the Reaction of Ethanol with Propylene Oxide

The reaction of ethanol with propylene oxide over calcined layered double hydroxides(CLDH) was investigated. The results show that CLDH has a good activity and a good selectivity, but the activity and the selectivity of CLDH decrease when CLDH reforms LDH- the so called 'memory effect'. The influence of the 'memory effect' on the CLDH returning to LDH was studied by the hydration reaction. It is shown that the 'memory effect' is not complete, and the decreases of the Mg/Al molar ratio of LDH and the crystallite size due to the increase of the hydration reaction time result in the drop of the activity and the selectivity.

China Calcined Bauxite Market Production and Outlook

The resources, mining capacity and calcination capacity of refractory grade bauxite in China market were introduced.Then major environmental protection regulations launched over the past years were briefly reviewed. Meanwhile some thoughts about the outlook of the market were shared.

Bovine Calcined Bone for the Repair of Radial Defect in a Rabbit Model

In order to investigate the bovine calcined bone's ability of repairing segmental bone defect and seek a new artificial bone substitute material, the bovine calcined bone (450℃,32 h) was implanted into the 10 mm middle radial defect of rabbits with tricalcium phosphate ceramics as the control. By using the methods of histology, radiology and biomechanics their osteogenic ability were measured. It was found that the bovine calcined bone's ability of repairing bone defect was better than that of tricalcium phosphate ceramics. The histological Nilsson′s scores at 3rd, 5th, 9th week after operation were significantly increased ( P <0.01). At 12th week after operation the bending strength of radius in experimental group was much higher than that of control group and turned normal. It was suggested that bovine calcined bone is an ideal artificial bone substitute material with good ability of repairing segmental bone defect and some degree of mechanical strength.

Influence of Reactive Alumina and Calcined Alumina on properties of Free Flowing Castables

Reactive alumina is a well-established group of raw materials for refractory castables to improve their rheological behavior.In this article the influence of bimodal reactive alumina and standard(<325#)calcined alumina on workability,packing density and strength of alumina based castables is examined.It will be shown that there is a significant effect on water demand and apparent density of the castable,which is depending on the percentage of reactive alumina on the one hand and on the type of reactive alumina on the other hand.The effect of the alumina on setting time and cold crushing strength has shown to be insignificant in this set of experiments.